Viscous coupling having an improved coolant system

ABSTRACT

A viscous coupling apparatus includes relatively rotatable input and output members configured so as to define a shear space therebetween so that the viscous fluid in the shear space transmits torque between the members. The transmission of torque results in the generation of heat. One of the members has a chamber for receiving a coolant medium for dissipating at least a portion of the generated heat. Means are provided for effecting substantially continuous flow of the coolant medium into and out of the chamber during transmission of torque and this means includes an inlet conduit for directing the coolant medium into the chamber and a separate outlet conduit for directing heated coolant medium from the chamber.

o '1 1 Unite States stem 1 1 1111 3,749,214 Leichliter 1 July 31, 1973VISCOUS COUPLING HAVING AN 3,062,347 11/1962 Hombostel 192 113 BIMPROVED COOLANT SYSTEM 3,505,982 4/1970 Walter et al. 192/1 13 B [75]Inventor: n'iaggle K. Lelchllter, Marshall, Primary Examiner Ana n D-Hermann A ttorney- Thomas L. Tarolli et a1 [73] Assignee: EatonCorporation, Cleveland, Ohio [22] Filed: Nov. 26, 1971 [57] ABSTRACT 2Appl' 202,209 A viscous coupling apparatus includes relatively rotatableinput and output members configured so as to define a shear spacetherebetween so that the viscous [52] 192/58 123/41'46' 192/113 B fluidin the shear space transmits torque between the [51] [Ill- Cl. F16635/00, Flfid 13/72 members The transmission of torque results in the[58] Field 01 Search 192/58 B, 1 13 B, eration f heat. o of the membersh a chamber for 123/4146 receiving a coolant medium for dissipating atleast a portion of the generated heat. Means are provided for [56]References cued effecting substantially continuous flow of the coolantUN TED S ATES PATEN S medium into and out of the chamber duringtransmis- 3,661,237 5/1972 Thompson 192/58 B on of to que and t is meansinc udes an inlet conduit 3,007,555 11/1961 Eames 192/113 B X fordirecting the coolant medium into the chamber and 2,699,846 1/1955 ma eta 192/58 B a separate outlet conduit for directing heated coolant Allen,.ll'

medium from the chamber 2,294,207- 8/1942 Roberts 192/ 1 13 B X2,852,118 9/1958 Lacroix, Jr. et al 192/113 8 7 Claims, 3 DrawingFigures 1.. M 52 2?, i 60 t2 v 62 r a) 72 3 a 2 4 v m 41% 44 Z 90 -f- 7/4' 28" 54 Y 26" a Z 22 PATENTEB JL'L31 191s SHEET 2 OF 2 f 0050. O a 0 IQ Flea VISCOUS COUPLING HAVING AN IMPROVED COOLANT SYSTEM This inventionrelates to the art of viscous couplings and, more particularly, to aviscous coupling having an improved cooling system.

Viscous couplings are well known and typically include relativelyrotatable input and output members configured so as to define a shearspace therebetween so that viscous fluid in the shear space transmitstorque between the members. Such a coupling is commonly used for drivinga cooling fan associated with the engine of an automobile. With theincreased horespower of automobile engines, as well as the reducedfrontal or ram air area and the use of smog control heat loads,automobile engine fan cooling requirements have been increased.

A significant problem in conjunction with modifying the design ofviscous couplings to handle higher fan cooling requirements is thedissipation of heat generated by the transmission of torque between theinput and output members of viscous couplings. As the temperature of aviscous coupling increases, the viscosity of the fluid in the shearspace between the input and output members decreases, and, consequently,a greater shear area is required to transmit an equivalent amount oftorque. By maintaining the viscous coupling at a lower temperature, itis possible to provide greater torque carrying capacities in thecoupling by maintaining the viscous fluid at a higher viscosity. Inaddition, the life of viscous fluid and bearings associated with thecoupling is increased when the viscous coupling is effectively cooled.

The present invention contemplates the provision of a viscous couplingemploying relatively movable input and output members configured so asto define a shear space therebetween. Viscous fluid contained in theshear space serves to transmit torque between the members duringrelative rotation thereof, with the transmission of torque resulting inthe generation of heat.

One of the members of the viscous coupling has a chamber for receiving acoolant medium for dissipating at least a portion of the generated heat,such as disclosed in copending application Ser. No. 878,136 now U.S.Pat. No. 3,661,237.

In accordance with the present invention, means are provided foreffecting substantially continuous flow of the coolant meduim into andout of the chamber during transmission of torque. This means includes aninlet conduit for directing coolant medium into the chamber and aseparate outlet conduit for directing heated coolant medium from thechamber. Moreover, the coolant circulating means includes a pump influid communication with the inlet and outlet conduits so as to providea pressure differential to assure positive pumping of the coolant mediuminto and out of the chamber.

The coolant receiving chamber is defined by walls configured so that aprimary heat transfer zone is located closer to the outlet from thechamber than to the inlet thereof, and the fluid flows across the wallarea defining the primary heat transfer zone immediately prior toexiting from the chamber. Moreover, the coolant receiving chamber isdivided by a flow directing baffle, and the cooling medium is directedinto the coolant receiving chamber on one side of the baffle, flowsaround the baffle, flows through the primary heat transfer zone on theother side of the baffle and then exits from the chamber. All of which,provides for a positive flushing action in the coolant receivingchamher.

As the coolant medium, a water glycol (anti freeze) mixture, contactsthe primary heat transfer area, certain amounts of the water vaporize,thereby absorbing a large amount of heat due to the change in state ofthe water. The glycol remains a liquid to a much higher temperature thanwater at an equivalent pressure, and an accumulation of glycol liquid incontact with the pri mary heat transfer zone would substantially destroythe phase change cooling effect by a change in state of the water. Thepositive pumping pressure and the flushing action provided by thepresent invention, prevent any substantial accumulation of glycol(anti-freeze) in the coolant chamber and assure a continuous effectiveheat transfer by vaporizing water flowing through the coolant receivingchamber.

Consequently, it is an object of the present invention to provide animproved viscous coupling constructed so as to dissipate heat generatedby the coupling during transmission of torque with the heat beingdissipated by recirculation of a coolant medium into and out of acoolant receiving chamber in one of the viscous coupling members inpositive effective manner which prevents substantial accumulation ofglycol in the coolant receiving chamber.

A still further object of the present invention is to provide improvedmeans for cooling a viscous coupling by providing a positive pressurepumping of coolant into and from a heat exchange chamber located in oneof the viscous coupling members and an effective flow of the fluidthrough the chamber to provide a positive flushing of the chamber by thefluid flow.

The foregoing and other objects and advantages of the invention willbecome more readily understood from the following description of thepreferred embodiment, taken in conjunction with the accompanyingdrawings in which:

FIG. 1 is a cross sectional view of an apparatus embodying the presentinvention;

FIG. 2 is an enlarged view of a portion of the apparatus of FIG. 1; and

FIG. 3 is a view taken along line 33 of FIG. 2.

Referring now to the drawings, there is illustrated the presentlypreferred embodiment of the present invention as comprising a viscouscoupling 10 used in conjunction with driving a fan 12 of an internalcombustion engine, such as that of an automobile. It is contemplatedthat the internal combustion engine be provided with a water pump,partially shown at 14, to circulate a cooling medium, such as a mixtureof water and antifreeze, around the engine to absorb heat created bycombustion in the engine, in a conventional manner. It is alsocontemplated that the internal combustion engine be provided with aradiator which, in a conventional manner, employs a plurality of thintubes through which the cooling medium flows. Air (ram air) is forcedthrough the radiator to cool the cooling medium which is thenrecirculated by the water pump 14 through the engine. The air is forcedthrough the radiator due in part to the forward movement of the vehicleas the exposed frontal area thereof allows air to flow through theradiator in accordance with the speed of the vehicle. Fan 12, in aconventional manner, serves to assist movement of air through theradiator, and at lower speeds the fan is required to move more airthrough the radiator. As is known, one characteristic of viscouscoupling is that the rotational output speed of the coupling will notincrease proportionately with an increase in the input speed of thecoupling. Consequently, as the speed of the vehicle increases the fan isnot driven at a proportionately increased speed. This characteristictakes advantage of the fact that at higher vehicle speeds fan speed cantail off due to the higher ram air flow through the radiator.

The viscous coupling includes an input coupling member 16 and an outputcoupling member 18 which are relatively rotatable about a common axis ofrotation AR. The radiator fan 12 is suitably secured to output member 18and rotates therewith about the axis of rotation AR. lnput member 16 isdrivingly connected to a drive member 20. Drive pulleys 22 are connectedto the drive member 20 and belts 24 are trained about the pulleys 22. Atleast one of the belts is driven, as from the crankshaft of theautomobile engine, to drive the fan and the other belts may function todrive other accessories.

The drive between the input and output members 16 and 18 of the viscouscoupling is effected by the action of viscous shear fluid positionedtherebetween. Output member 18 has a plurality of grooves 26 definedtherein which receive fins 28 extending from the input member 16 in aconventional manner. The opposing surfaces of members 16 and 18 arespaced slightly to provide a fluid shear space therebetween. This spaceis, for all practical purposes, confined to the area of grooves 26 andfins 28 so as to define an annular shear space 30 which is coaxial aboutaxis of rotation AR. Viscous fluid is contained in this shear space sothat when input member 16 is rotated the viscous fluid transmits torqueto the output member to which the fan 12 is secured. The output member18 is rotatably mounted on drive member 20 by a suitable bearing 32 sothat the output member may rotate relative to the input member aboutaxis of rotation AR.

The annular shear space 30 represents a portion of a working chamber 34containing viscous fluid. The input member 16 rotates in this workingchamber 34 and, as is well known, the amount of torque transmitted fromthe input member to the output member 18 is a function of the volume andviscosity of the fluid in chamber 34 and, more specifically, in theshear space 30. in the event that fluid is not located in the shearspace, no torque will be transmitted between the input and outputmembers. Preferably, coupling 10 employs means to vary the volume offluid in working chamber 34 including means providing fluid flow intoand out of the working chamber from a reservoir chamber 36. Reservoirchamber 36 is defined by a plate 38 and a disc-shaped cover 40 which aresecured to output member 18 as by rolling over an annular lip portion 42of the output member to secure plates 38 and 40 in position. Means areprovided for effecting fluid flow between chambers 34 and 36. Thismeans, for example, may be constructed as shown in the US. Pat. to A.Sutaruk No. 3,263,783, assigned to the same assignee as the presentinvention. Briefly, such a fluid control means includes a helicallywound bimetallic temperature responsive coil 44 having one endpositioned in a slot formed in a stub shaft 46 rotatably supported bycover plate 40 coaxial with axis of rotation AR.

During the transmission of torque between input member 16 and outputmember 18, the viscous fluid in shear space 30 is sheared. Thisgenerates heat and the heat decreases the viscosity of the viscousfluid. As the viscosity decreases, the coupling transmits less torqueand, hence, fan 12 rotates at a proportionally slower speed with respectto the speed of the motor. In order to dissipate the generated heat, oneof the coupling members is constructed so as to be liquid cooled. Asdepicted in the embodiment illustrated herein, the input coupling member16 is configured so as to define a chamber 50. As will be developed ingreater detail hereinafter, this chamber serves to receive coolingmedium, such as a mixture of water and antifreeze, from a suitablesupply source, such as the radiator associated with an automobileengine. This cooling medium is vaporizable at the normal operatingtemerature of coupling 10. Chamber 50 is closed by a cover plate 52 aswith the use of machine screws 54. An 0-ring 56 serves to provide afluidtight seal between input member 16 and cover plate 52.

In accordance with the present invention, both an inlet and an outletare provided for chamber 50 so that the cooling medium may be pumpedinto the chamber and then exit therefrom through the outlet. In theembodiment illustrated, drive member 20 is hollow defining a passagewaycoaxial with axis of rotation AR. Within this passageway there isprovided a sleeve member 60 positioned so as to be coaxial about axis ofrotation AR. Sleeve member 60 serves as the inlet conduit through whichthe cooling medium flows into the chamber 50. One end 62 of sleevemember 60 extends slightly more than halfway into chamber 50. Adiscshaped baffle plate 64 is secured to sleeve 60 at one end 62, as bywelding. The circumferential edge of baffle plate 64 is secured atannular spaced apart locations to input coupling member 16. This isaccomplished with an annular array of spaced apart flanges 66 extendingfrom the circumferential edge of plate 64 and secured as by welding tomember 16. These flanges 66 are spaced apart in an annular array so thatspaces 66a (FIG. 3) are provided therebetween for the cooling medium toflow from the inlet side 50a of baffle plate 64 to the outlet side 50bthereof. The outlet conduit for chamber 50 is provided by the remainingportion of the passageway in drive member 20. Drive member 20 isprovided with a flared annular opening 68 through which cooling mediumexits from the chamber.

As noted, baffle plate 64 devides chamber 50 into inlet portion 50a andoutlet portion 50b. in addition, the interior walls of input couplingmember 16 are configured to define an annular recess 70. The outletportion 50b of chamber 50 is substantially larger than the inlet portionand serves and the primary heat transfer zone. As the cooling mediumflows over the surfaces defining the chamber portion 5%, heat isabsorbed thereby and due to the circulation of the medium, the heat isremoved from the viscous coupling.

The invention contemplates that a positive pressure differential beprovided between the inlet and outlet conduits for chamber 50 so thatthe cooling medium is pumped through sleeve 60 to its open end 62 andinto the inlet portion 50a of chamber 50. It is also contemplated thatdrive member 20 be driven about axis of rotation AR as by use of pulleys22 driven from the crankshaft of an automobile engine so that as thecooling medium enters chamber 50 it is driven radially outward and thenflows into the larger outlet portion 50b of chamber 50 through thespaces between adjacent baffle flanges 66. As the cooling medium passesthrough this larger portion of chamber 50 which serves as the primaryheat transfer zone, heat generated by coupling is transferred to thecooling medium. As the cooling medium preferably employs a mixture ofwater and antifreeze, the water will absorb heat and vaporize. Theantifreeze concentrate, together with the water vapor, will be flushedout of chamber 50 through the outlet 68 and thence through the annularpassage in drive member 20 by the positive and continuous flow ofcoolant around the baffle 64 and through the chamber portion 50b.Accordingly, there is no tendency for any build-up of concentratedantifreeze (glycol) in the chamber 50b. The mixture of water, watervapor and antifreeze concentrate flushed from the chamber portion 50b isrecirculated through a reservoir, as with a suitable pumping means,where the water vapor will condense as it cools to restore normaldilution of the water-anitfreeze mixture before this cooling medium isthen recirculated back into chamber 50 through sleeve 60.

As stated hereinbefore, it is contemplated that the viscous coupling 10be employed for driving fan 12 in an internal combustion engine.Consequently, the coupling may be mounted so as to be driven by a pulley22 with suitable fastner assemblies 71. The cooling system may receive acooling medium from various reservoirs and it is contemplated that theinlet 62 and outlet 68 of chamber 50 be in fluid communication with sucha reservoir and a suitable pump. In the embodiment illustrated, thereservior of cooling medium is the radiator system of an internalcombustion engine, and the pump takes the form of water pump 14.Consequently, drive member 20 is secured to a sleeve member 72, as witha press fit. The sleeve member 72 extends coaxially about axis ofrotation AR and serves to carry at one end the impeller 74 of water pump14. Impeller 74 is suitably secured to sleeve 72 as by a press fit orother suitable securing means so that as drive member 20 is driven,sleeve member 72 rotates therewith to in turn drive the impeller 74 in aknown fashion. The water pump 14 conventionally includes a housing 76which carries a suitable ball bearing arrangement 78 between acylindrical inner wall of the housing and the outer cylinderical surfaceof sleeve member 72. As is conventional, the water pump housing 76 isprovided with an inlet 80 for receiving the cooling medium from theradiator, as with a suitable hose, with the inlet leading to an enlargedannular chamber 82 in which impeller 74 rotates. An outlet (not shown)carries the cooling medium, as pumped by impeller 74, through the engineblock and another radiator hose for recirculation. Chamber 82 is closedat one end by a suitable wall 84. A variable shaped seal ring 86provides a seal between wall 84 and housing 76 so as to define afluidtight space 88 between the impeller 74 and wall 84.

In accordance with the present invention, inlet sleeve 60 is secured asby a press fit to an elongated conduit member 90 which extends coaxiallythrough sleeve member 72 and is supported at one end thereof by coiledsprings 92 and at the opposite end thereof by an annular support 94.Sleeve member 90 and support 94 are flared outwardly to provide an inletto receive the cooling medium from the chamber 82 through the space 88.

In order to provide an effective positive pressure differential betweenthe inlet 50a and outlet 50b of chamber 50, a cross-drilled aperture 96is provided in the impeller' 74 in registry with an aperture 98 insleeve member 72 by an annular groove X in impeller 74. Also the properspace relationship between the back surface of impeller 74 (surface Y)and surface Z of wall 84 must exist. Preferably, this aperture andimpeller space relationship arrangement is sufficient to ensure at leasta twenty-pound per square inch differential pressure between the inletand outlet conduits.

In the operation of the lfuid coupling 10, heat is generated during thetransmission of torque from the input coupling member 16 to the outputcoupling member 18. The transmission of torque results in the generationof heat which, if not dissipated, results in loss of viscosity of theviscous fluid in the working chamber containing the shear space 30. Ifthe viscous fluid is not effectively cooled, a loss in transmission oftorque will result. Consequently, in accordance with the presentinvention, the chamber 50 is provided in the input coupling member 16and this chamber is partitioned by the baffle 64 so as to provide aninlet chamber portion and an outlet chamber portion. The outlet chamberportion is substantially larger than the inlet chamber portion andserves as the primary heat transfer zone. A cooling medium, such as amixture of water and antifreeze, is circulated through chamber 50 bypositive pressure flow with the use of water pump 14. This coolantmedium flows into the inlet chamber portion from the inlet conduitformed by members and 60. Since the input member is rotating, baffleplate 64 will assist in directing the coolant medium radially outwardwhich will then enter the outlet chamber 5012 through the spaces betweenadjacent flanges 66 of the baffle plate 64. As the cooling medium flowsinto the outlet chamber portion, heat is received from the primary heattransfer zone. Depending on the working temperature, the water will atleast in part vaporize leaving concentrated antifreeze. This mixture ofwater vapor and concentrated antifreeze is, however, flushed out of theoutlet chamber 5011 due to the positive pumping and flushing action andexits from the chamber through outlet 68. Outlet 68 is an annularpassageway between the inner walls of drive member 20 and the outerwalls of sleeve 60. This passageway continues through sleeve 72 wherethe mixture of water vapor and concentrated antifreeze exits throughaperture 98 in sleeve 72 and then through the cross-drilled aperture 96in the impeller 74. During the flow of the mixture, the water vaporcondenses to dilute the anitfreeze concentrate to obtain a normalmixture of water and antifreeze as the cooling medium is recirculated bythe impeller 74 through the radiator of the automobile and thencedirected back to chamber 50 through sleeve 90. This pumping processserves to continuously cause flushing of the concentrated antifreeze andwater vapor from the outlet chamber 50b during the operation of thefluid coupling.

Although the invention has been described herein with respect to apreferred embodiment, it will be apparent to those skilled in the artthat various modifications and arrangements of parts may be made to thefluid coupling and antifreeze water flushing system within the spiritand scope of the appended claims.

What is claimed is:

1. An apparatus comprising relatively rotatable input and outputcoupling members, said input and output coupling members defining ashear space therebetween so that viscous fluid in said shear spacetransmits torque between said members with said transmission of torqueresulting in the generation of heat, one of said members having achamber for receiving a coolant medium for dissipating at least aportion of the generated heat, at least a portion of said coolant mediumvaporizing upon absorbing heat from said one member, inlet conduit meansfor directing the coolant medium into said chamber, outlet conduit meansfor directing the coolant medium from said chamber, means in saidchamber for directing coolant medium through said chamber to provide aflushing thereof, coolant recirculating means including pump means influid communication with said inlet and outlet means so as to provide apositive pressure differential for pumping coolant medium through saidchamber, a hollow rotatable shaft having a passageway therein forreceiving coolant medium from said outlet means, said pump meansincluding walls defining a pump chamber and an impeller mounted on saidshaft for rotation in said pump chamber, and means defining a conduitthrough said shaft and said impeller for coolant medium to flow fromsaid passageway through said impeller conduit to said pump chamber.

2. An apparatus as set forth in claim 1 wherein said hollow shaft isconnected to said one coupling member for rotation therewith about acommon axis of rotation and said impeller conduit is configured so as tobe directed substantially radially outward from said shaft and throughsaid impeller to said pump chamber.

3. An apparatus set forth in claim 1 including a tubular member mountedwithin said shaft for fluid communication at one end with said inletmeans and at said other end with said pump chamber for receivingrecirculated coolant medium therefrom.

4. A viscous fluid coupling apparatus comprising relatively rotatableinput and output members configured so as to define a shear spacetherebetween so that viscous fluid in said shear space transmits torquebetween said members with the transmission of torque resulting in thegeneration of heat, means supporting said input and output members forrotation about a common axis, one of said members having wall meansdefining a heat exchange chamber for receiving a coolant mediumcomprising a water-glycol mixture to dissipate at least a portion ofsaid generated heat, the water in the waterglycol mixture vaporizing insaid heat exchange chamber, said shear space and said chamber being eachannular and coaxial about said axis of rotation with said chamber beinglocated radially inward from said shear space, baffle means forpartitioning said chamber into an inlet chamber portion and a largeroutlet chamber portion so that the latter serves as a primary heattransfer zone, said baffle means comprising a member positionedcoaxially of said input and output members and having a radiallyextending portion which partitions said chamber, inlet means fordirecting the waterglycol mixture into said inlet chamber portion, saidradially extending portion defining passage means for said water-glycolmixture to flow from said inlet chamber portion to said outlet chamberportion, outlet conduit means communicating with said outlet chamberportion through which said water-glycol mixture may exit from saidchamber, said outlet conduit means comprising a hollow drive shaft fordriving said one member and wherein said drive shaft has a passagewaytherethrough in fluid communication with said outlet chamber portion,and a tubular member in said passageway with said tubular member servingas said inlet means to said chamber and the remaining portion of saidpassageway about said tubular member serving as said outlet means fromsaid chamber, and pump means in fluid communication with said inlet andoutlet conduit means to provide a positive pressure differential to pumpthe water-glycol mixture therethrough and thereby minimize concentrationof glycol in said heat exchange chamber where water in the mixturevaporizes.

5. An apparatus as defined in claim 4 wherein said pump includes animpeller rotatable in a pump chamber to effect said pumping action andfurther including means defining a conduit through said hollow driveshaft and said pump impeller for the water-glycol mixture to flow fromsaid outlet conduit through said impeller to said pump chamber.

6. An apparatus as defined in claim 4 wherein said baffle meanscomprises a single disc member having spaced outer peripheral portionswhich engage said wall means and said passage means defined by saidradially extending portion being located intermediate said spacedperipheral portions of said disc so that the water-glycol mixture flowsacross said wall means to thereby minimize the concentration of glycolalong said wall means.

7. A viscous fluid coupling apparatus comprising relatively rotatableinput and output members configured so as to define a shear spacetherebetween so that viscous fluid in said space transmits torquebetween said members with the transmission of torque resulting in thegeneration of heat, means supporting said input and output members forrotation about a common axis, one of said members having wall meansdefining a heat exchange chamber for receiving a coolant mediumcomprising a water-glycol mixture to dissipate at least a portion ofsaid generated heat, the water in the waterglycol mixture vaporizing insaid heat exchange chamber, said shear space and said chamber being eachannular and located about said axis of rotation, baffle means forpartitioning said chamber into an inlet chamber portion and an outletchamber portion, inlet means for directing the water-glycol mixture intosaid inlet chamber portion, said baffle means defining passage means forsaid water-glycol mixture to flow from said inlet chamber portion tosaid outlet chamber portion, outlet conduit means communicating withsaid outlet chamber portion through which said water-glycol mixture mayexit from said chamber, and inlet conduit means for directing saidwater-glycol mixture to said inlet chamber portion, and pump means influid communication with said inlet and outlet conduit means to providea positive pressure differential to pump the water-glycol mixturetherethrough and thereby minimize concentration of glycol in said heatexchange chamber where water in the mixture vaporizes.

I i a i l

1. An apparatus comprising relatively rotatable input and outputcoupling members, said input and output coupling members defining ashear space therebetween so that viscous fluid in said shear spacetransmits torque between said members with said transmission of torqueresulting in the generation of heat, one of said members having achamber for receiving a coolant medium for dissipating at least aportion of the generated heat, at least a portion of said coolant mediumvaporizing upon absorbing heat from said one member, inlet conduit meansfor directing the coolant medium into said chamber, outlet conduit meansfor directing the coolant medium from said chamber, means in saidchamber for directing coolant medium through said chamber to provide aflushing thereof, coolant recirculating means including pump means influid communication with said inlet and outlet means so as to provide apositive pressure differential for pumping coolant medium through saidchamber, a hollow rotatable shaft having a passageway therein forreceiving coolant medium from said outlet means, said pump meansincluding walls defining a pump chamber and an impeller mounted on saidshaft for rotation in said pump chamber, and means defining a conduitthrough said shaft and said impeller for coolant medium to flow fromsaid passageway through said impeller conduit to said pump chamber. 2.An apparatus as set forth in claim 1 wherein said hollow shaft isconnected to said one coupling member for rotation therewith about acommon axis of rotation and said impeller conduit is configured so as tobe directed substantially radially outward from said shaft and throughsaid impeller to said pump chamber.
 3. An apparatus set forth in claim 1including a tubular member mounted within said sHaft for fluidcommunication at one end with said inlet means and at said other endwith said pump chamber for receiving recirculated coolant mediumtherefrom.
 4. A viscous fluid coupling apparatus comprising relativelyrotatable input and output members configured so as to define a shearspace therebetween so that viscous fluid in said shear space transmitstorque between said members with the transmission of torque resulting inthe generation of heat, means supporting said input and output membersfor rotation about a common axis, one of said members having wall meansdefining a heat exchange chamber for receiving a coolant mediumcomprising a water-glycol mixture to dissipate at least a portion ofsaid generated heat, the water in the water-glycol mixture vaporizing insaid heat exchange chamber, said shear space and said chamber being eachannular and coaxial about said axis of rotation with said chamber beinglocated radially inward from said shear space, baffle means forpartitioning said chamber into an inlet chamber portion and a largeroutlet chamber portion so that the latter serves as a primary heattransfer zone, said baffle means comprising a member positionedcoaxially of said input and output members and having a radiallyextending portion which partitions said chamber, inlet means fordirecting the water-glycol mixture into said inlet chamber portion, saidradially extending portion defining passage means for said water-glycolmixture to flow from said inlet chamber portion to said outlet chamberportion, outlet conduit means communicating with said outlet chamberportion through which said water-glycol mixture may exit from saidchamber, said outlet conduit means comprising a hollow drive shaft fordriving said one member and wherein said drive shaft has a passagewaytherethrough in fluid communication with said outlet chamber portion,and a tubular member in said passageway with said tubular member servingas said inlet means to said chamber and the remaining portion of saidpassageway about said tubular member serving as said outlet means fromsaid chamber, and pump means in fluid communication with said inlet andoutlet conduit means to provide a positive pressure differential to pumpthe water-glycol mixture therethrough and thereby minimize concentrationof glycol in said heat exchange chamber where water in the mixturevaporizes.
 5. An apparatus as defined in claim 4 wherein said pumpincludes an impeller rotatable in a pump chamber to effect said pumpingaction and further including means defining a conduit through saidhollow drive shaft and said pump impeller for the water-glycol mixtureto flow from said outlet conduit through said impeller to said pumpchamber.
 6. An apparatus as defined in claim 4 wherein said baffle meanscomprises a single disc member having spaced outer peripheral portionswhich engage said wall means and said passage means defined by saidradially extending portion being located intermediate said spacedperipheral portions of said disc so that the water-glycol mixture flowsacross said wall means to thereby minimize the concentration of glycolalong said wall means.
 7. A viscous fluid coupling apparatus comprisingrelatively rotatable input and output members configured so as to definea shear space therebetween so that viscous fluid in said space transmitstorque between said members with the transmission of torque resulting inthe generation of heat, means supporting said input and output membersfor rotation about a common axis, one of said members having wall meansdefining a heat exchange chamber for receiving a coolant mediumcomprising a water-glycol mixture to dissipate at least a portion ofsaid generated heat, the water in the water-glycol mixture vaporizing insaid heat exchange chamber, said shear space and said chamber being eachannular and located about said axis of rotation, baffle means forpartitioning said chamber into an inlet chamber portion and an outletchamber portion, inlet means for directing thE water-glycol mixture intosaid inlet chamber portion, said baffle means defining passage means forsaid water-glycol mixture to flow from said inlet chamber portion tosaid outlet chamber portion, outlet conduit means communicating withsaid outlet chamber portion through which said water-glycol mixture mayexit from said chamber, and inlet conduit means for directing saidwater-glycol mixture to said inlet chamber portion, and pump means influid communication with said inlet and outlet conduit means to providea positive pressure differential to pump the water-glycol mixturetherethrough and thereby minimize concentration of glycol in said heatexchange chamber where water in the mixture vaporizes.